Two essential principles for alignment of wheelset and wheelset truing machine are generally known. In the first principle, the wheelset axle is assumed as basis e.g. center bore, axle centering chuck, centering at dimensionally suitable housing. The second principle is based upon the wheels located in supporting rollers provided in prismatic arrangement.
Upon alignment of wheelset with regard to the wheelset truing machine by means of supporting rollers as described in the leaflet "Variofect DRU Underfloor Wheelset Lathe" of Hoesch Maschinenfabrik Germany AG and protected by patents EP 195 891 and DE-GM 85 09 180, alignment can only be done in vertical plane due to the oblique position of vehicle with regard to the wheelset truing machine with the effect that only three out of four rollers are bearing on the two wheels of wheelset to be machined. Thus, the aligning effect of the prisms obtained by the two supporting rollers is lost. Being aware of this, additional live center points for centering the wheelset at the center bores of wheelset axle were proposed in the example of DE-PS 39 02 550 and EP 380 919.
Alignment on the basis of center bores of wheelset is shown in the leaflets of the company Simmons Machine Tool Corp. An ideal solution for alignment of wheelset and wheelset truing machine in two planes is introduced here in a quite ideal way. However, the necessity of clearing the center bores has a disadvantageous effect.